Help for interpretation of our measuring results

General

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Optical assessment using microscopy

Surface structure

The microscope photos clearly show deposits and encrustations. If necessary, a solubility test with HCl is carried out to differentiate between inorganic hydroxides and the like, and biological growth.

At high portions of fractured beads, pressure loss or nozzle obstruction with channel forming in the resin bed are usual consequences.

There is also the risk that cation exchange splinters get into the anion exchanger stage and there cause poor washout as well as increased conductivity, in particular during start-up. This effect depending on the extent of cation exchanger splinters often is irreversible and has to be detected in time.

In the counting of the fracture components, often only relatively small numbers are given, e.g. 5…10%. These, hover, often signify a drastic limitation, since smaller fragments must be put together approximately into whole beads during the counting process. In the case of usually smaller fragments, the resin bed can thus be interspersed with splinters, which can have drastic consequences.

The most commonly known characteristic is the volumetric total capacity, which can be found in the data sheet of the resins delivery form. Usually in addition to our measuring data we state the percentage loss relative to the new specification

This capacity value, in conjunction with the volume-related capacity, provides information about the ageing state of the sample.

Cation exchangers do not lose their groups, which can be seen in very consistent dry capacity values. If at the same time volume-related capacity decreases, weakening of the resin matrix by decrosslinking (with a volume increase resulting therefrom) must be concluded.

In the case of anion exchangers, a reduction of the initial 4.5 and 5 eq/kg is observed over the years, which can reach as low as 3 eq/kg and lower. This decrease largely corresponds to the decrease in the volume-related TC and indicates that the resin structure (the resin matrix) hardly suffers, but the functional groups are released over time.

Quaternation level (strong basic portion of the total capacity, only strong basic and mixed basic types)

One can set the following order of precedence from the sensitivity to ageing effects: Strong basic type 2 groups > strong basic type 1 groups >> weak basic groups. At the same time, type 2 groups become weak basic groups due to ageing. Type 1 groups are often completely lost.

From the ratio of strong basic to weak basic groups quite a good measure of the extent of ageing can be derived.
The degree of quaternation, the proportion of the strong base to the sum of all basic groups, is introduced here.